The invention relates to pile driving, and more particularly, but not exclusively, to underwater pile driving, e.g. for stabbing piles directly into the seabed.
It is known to provide a guide for aligning a pile with the surface of a substrate into which the pile is to be driven and to provide stability for a piling hammer. Particularly when piling underwater there is the problem that after the pile has been introduced into the seabed or the like, the guide must be removed to allow the pile to be driven into its final position. This guide removal is time consuming and thus expensive.
It is an object of the invention to provide a stabilising guide for a pile which can be moved out of the way after a pile has first been established in its substrate to enable the pile driving to continue to drive the pile into its final position without any need to stop the driving to remove the guide.
According to a first aspect of the invention a pile guide comprises a guide member adapted to be supported on a substrate into which the pile is to be driven, means mounting the guide member in an operative position in which it can support a pile and hammer and permitting movement of the guide member into an inoperative position in which the guide member is remote from the pile, and latch means for holding the guide member in its operative position, the latch means co-operating with means on or associated with the pile to unlatch the guide member after the pile has been inserted to a predetermined extent to allow the guide member to move to its inoperative position.
The guide member may comprise a pair of generally semi-cylindrical members which together form a tubular member for enclosing the pile.
The guide member may be hinged on the mounting means. Thus the pair of semi-cylindrical members may be hinged on the mounting means at their bottom ends so that they move away from the pile in opposed directions. Means for moving the guide member into its inoperative position, e.g. spring means, may be provided but preferably the guide member is urged into its inoperative position by gravity.
The pile guide may comprise lifting means which also causes the pile guide member to assume its operative position.
The means on the pile to unlatch the guide member may comprise a detent member attached (e.g. welded) to the pile.
The mounting means may comprise a base frame adapted to rest on the substrate (e.g. seabed) to support the guide member in position. The base frame may surround the guide member. The base frame may, however, be formed with an aperture or slot extending therethrough to facilitate removal of the pile guide from rigging or a tether attached to a pile driven into the seabed. The guide member may have groove means for receiving rigging or a tether attached to a pile passing through the guide member.
In accordance with a second aspect of the present invention, there is provided a method of driving a pile into a substrate, comprising: providing a pile guide in accordance with the first aspect of the present invention; providing means on or associated with the pile to unlatch the guide member after the pile has been inserted to a predetermined extent to move the guide member to its inoperative position; supporting the pile with the guide member in the operative position; and driving the pile into the substrate to an extent beyond the predetermined extent without removing the pile guide.
In accordance with a further aspect of the present invention, there is provided a pile guide comprising a guide member adapted to be supported on substrate into which a pile is to be driven, characterised in that the guide member comprises at least two parts, and by comprising means for moving the at least two parts between an operative position for supporting the pile and hammer and an inoperative position remote from the pile when the pile has been driven into the substrate to a predetermined extent. In the inoperative position, there is sufficient clearance to avoid the hammer fouling the at least two parts when the pile is driven beyond the predetermined extent, without the need to remove the pile guide itself.
The pile guide may further comprise a means for retaining the at least two parts in the operative position, the at least two parts having biasing means which urge the at least two parts into the inoperative position when the retaining means is disengaged. The retaining means may comprise latch means for latching the at least two parts together in the operative position, the latching means co-operating with trigger means on or associated with the pile to unlatch the at least two parts when the pile has been driven into the substrate to the predetermined extent. The biasing means may comprise counter weights which act under gravity.
The invention thus provides a simple mechanism which avoids the downtime required by conventional guides in removing the guide frame or piling hammer part way through the pile driving process.